textproduct: Albany

WHAT HAS CHANGED

As of 9:25 PM EST...Forecast was adjusted to lower temps a degree or two, placing most areas except the I-84 corridor at or below freezing. Temperatures only drop a few more degrees tonight, but this will allow any untreated surfaces to re- freeze. Also increased PoPs outside of the Mid Hudson Valley and southwestern New England where radar shows moderate snow currently ongoing, and expected to continue to push E/SE over the next few hours. 00z KALY sounding shows that the warm nose aloft has pretty much eroded thanks to approaching upper trough, so have changed precip types back over to mainly snow through the rest of the night. The only exception is across southwestern New England, where some light freezing drizzle remains possible through the next hour or two due to lack of cloud ice here out ahead of the main batch of precip.

Given the above forecast trends, SPS to highlight potentially slippery travel conditions was issued through 06z for all zones not already in the advisory or warning. This SPS may very well be extended in time through early this morning as we continue to evaluate radar and temperature trends. Still expecting snow to begin to taper to lighter snow showers around or shortly after midnight. Other than these changes through the next 6-10 hrs, previous forecast remains on track with more details in the previous discussion below...

KEY MESSAGES

1) Periods of wintry mix including snow, sleet, and freezing rain for eastern New York and western New England through tonight with lingering snow showers continuing tomorrow. Use caution if traveling during today's evening commute.

2) Continuing to monitor a strong coastal storm leading to winter weather impacts Sunday afternoon into Monday. There is a 30 to 70% chance for at least 4 inches of snow mainly south of I-90.

DISCUSSION

KEY MESSAGE 1...

We continue to monitor a second period of snow this evening as the main parent closed low tracks eastward. Increasing cyclonic vorticity advection will contribute to more widespread precipitation developing this evening mainly from 00 to 03 UTC through 06 UTC or snow. Cooler air advecting eastward will likely allow precipitation to fall as mainly snow with additional light snow accumulations expecting 0.5 to 2 inches mainly from I-90 northward with less south. After 06 UTC, the parent cyclone continues to track eastward as it becomes sheared out but the lingering moist/cyclonic flow regime should maintain scattered snow showers overnight, especially in favored upslope areas of the southern Adirondacks, southern Greens, Taconics and Berkshires. These snow showers should wind down tomorrow morning.

The brief break from snow showers continue into the early afternoon hours but with moist and confluent flow overhead and a weaker shortwave tracking overhead tomorrow afternoon into the evening, additional areas of snow showers look to develop and expand eastward, even outside of the favored upslope areas. Snow may turn steady at times given a weak sfc low that tracks overhead but with temperatures warming into the mid to upper 30s, valley area should see little if any additional accumulation; However, the hill towns and higher terrain (especially north of I-90) should see an additional coating to 1 inch of snow. Highest chance for additional snow accumulations look to be later Saturday afternoon into the evening as temperatures cool.

KEY MESSAGE 2...

We continue to monitor a strong coastal storm for Sunday afternoon into Monday with the latest guidance trending slightly further north and west with the storm track. However, most ensemble members still keep the coastal low staying near or just east of the classic 40N/70W benchmark. This is a notable benchmark for the I-95 corridor but does usually mean our southern zones mainly south of I-90 could receive light to moderate snow accumulations. The culprit for this storm is a potent shortwave trough that will track through the Midwest and deepen as it phases with a southern stream shortwave over the Ohio/TN Valley. Exactly when these shortwaves phase will be an important piece of the forecast puzzle as there is strong consensus that a secondary coastal low quickly develops off the coast of the Carolinas and undergoes rapid cyclogensis. The latest cluster analysis show that the timing and location of the phasing is the main driving factor in ongoing model differences in QPF/snowfall amounts. Should phasing occur earlier, the resulting coastal low would likely take on a more north and westerly track resulting in higher QPF/snowfall amounts. However, this solution is heavily favored by the GFS/GEFS and represents nearly 70% of the cluster solution that favors this output. On the other hand, the ENS and GEPS suggests phasing takes place late enough that the resulting coastal low slides slightly east of the 40N/70W benchmark and therefore keeps the higher QPF/snowfall amounts mainly south of the mid- Hudson Valley with just 10-25% chance for at least 0.2" of QPF during the 24 hour window from 1PM Sunday to 1PM Monday.

There are impressive dynamics at play including a notable dual jet structure that can potentially lead to a "bomb cyclone" so we will keep a close eye on trends. For planning purposes, there is a 30 to 60% chance for at least 4 inches of snow mainly near and south of I-90 during the 48 hr period from 7AM Sun to 7AM Tues which equates to winter weather advisories. There is also a 20 to 30% chance for moderate impacts (hazardous driving conditions and disruptions to daily life) per the probabilistic Winter Storm Severity Index focused mainly in Ulster, Dutchess and Litchfield County with less than 20% chance closer to I-90.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

Through 06z/Sun...Snow shower activity will decrease in coverage for the remainder of the overnight at the TAF sites. Have included TEMPO groups at KALB/KGFL/KPSF for any remaining snow showers with IFR/MVFR cigs/vsbys until 08z/Sat. Behind a frontal boundary, a gradual return to MVFR if not VFR conditions are likely, but there is some uncertainty whether or not any low stratus remains at some sites. Upslope flow developing at KPSF could bring a return to MVFR cigs and IFR/MVFR vsbys in any returning snow showers between 10-13z/Sat.

Some additional snow showers could bring periods of IFR vsbys to KALB/KGFL/KPSF Saturday afternoon and evening with cigs looking to trend back to MVFR. Some snow showers could also return to KPOU after 00z/Sun. Light to calm winds overnight will become west to northwesterly on Saturday becoming light to calm again Saturday night.

Outlook...

Sunday Night: Moderate Operational Impact. Breezy. Chance of SN. Monday: Moderate Operational Impact. Breezy. Chance of SN. Monday Night: Low Operational Impact. Breezy. NO SIG WX. Tuesday: Low Operational Impact. Breezy. NO SIG WX. Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: Moderate Operational Impact. Chance of RA...SN. Wednesday Night: Moderate Operational Impact. Likely RA...SN. Thursday: Moderate Operational Impact. Chance of RA...SN.

ALY WATCHES/WARNINGS/ADVISORIES

CT...Winter Weather Advisory until 7 AM EST this morning for CTZ001- 013. NY...Winter Weather Advisory until 7 AM EST this morning for NYZ032- 038>041-043-047>051-054-058-061-063-066-082-084. Winter Storm Warning until 1 PM EST this afternoon for NYZ033- 042-083. MA...Winter Weather Advisory until 7 AM EST this morning for MAZ001- 025. VT...Winter Storm Warning until 1 PM EST this afternoon for VTZ013>015.